Frequently -- and the good "development" theories define what they are "developing" before they start. Otherwise they are operating "with a blank check" that can be filled in by any and every investigator...
It was once believed that life could come from nonliving things, such as mice from corn, flies from bovine manure, maggots from rotting meat, and fish from the mud of previously dry lakes.
http://www.infoplease.com/cig/biology/spontaneous-generation.html
Why, I've even seen beautiful crystals grow from a liquid!
Add that to your "Theory of the evolution of [undefined] "life"...
I suppose it must have been very confusing for Darwin's contemporaries to read his theory, and then go to the dictionary looking for the word "life", and finding nothing.